Thyrotoxic Periodic Paralysis With Features of Andersen-Tawil Syndrome: A Case Report and Literature Review.

Thyrotoxic periodic paralysis (TPP) is a rare manifestation of hyperthyroidism. The pathophysiology of hyperthyroidism causing periodic paralysis involves the Na+/K+ ATPase and potassium channels. We present a case of a 30-year-old male who presented to the ED with acute onset of upper and lower limb weakness. The patient was found to have bilateral weakness in the upper and lower limbs, orbital hypertelorism, and mandibular hypoplasia. He was also found to have hypokalemia, low thyroid-stimulating hormone (TSH), elevated thyroid peroxidase antibody, and elevated thyroid-stimulating immunoglobulins. The patient's EKG was remarkable for a prolonged QTc interval. The patient regained his muscle strength after potassium replacement in less than 24 hours. He was started on methimazole and potassium supplements. Our case is unique because it shows the possibility of the presence of Andersen-Tawil syndrome (ATS) (long QT syndrome 7), diagnosed by the presence of periodic paralysis, long QT, and dysmorphic facial features with TPP. In conclusion, thyrotoxicosis can trigger ATS; also the two syndromes can co-exist owing to the similarity in their pathophysiology.